Post by The Astronomer on Apr 24, 2017 9:09:57 GMT

I started to wonder about this when I started switching my spacecraft fuel from methane to RP-1. Noble gasses were chosen as ion drive fuel in real life due to their inert nature. I wonder which other reaction masses can be used in these drives.

Post by bigbombr on Apr 24, 2017 16:28:21 GMT

Not sure what would be useful IRL, but in-game, I use methane for both MPDT's and NTR's. Noble gasses and hydrocarbons both seem to perform decently in MPDT's. I simply use methane because it's versatile, cheap and can realistically and easily be mass produced (producing methane out of hydrogen and CO2 seems easier than extracting noble gasses out of the atmosphere or rocks).

Post by Rocket Witch on Apr 26, 2017 5:39:35 GMT

In ion propulsion as a whole, certain easily-melted and highly-reactive metals were used before, namely caesium and mercury. Lithium MPTDs have also been test-fired, which is apparently pretty much the best fuel for them. Wikipedia lists hydrogen, bismuth, and iodine as other propellants that have been flown on a table near the bottom of its ion thruster page, though only lists hydrogen being used by MPDTs specifically.

My lithium thread was pretty well known, but I did also mod caesium in during March.

Would there be unwanted effects from using hydrocarbons on our potentially reactive MPD materials? And about the erosion mentioned by qswitched? I'm curious abut that part.

Presumably carbon deposits getting stuck around the engine and impeding its function over time, as with other engine types using hydrocarbons. Considering how small the engines are, it seems perfectly reasonable to bring a lot of spares even in engines that corrode quickly.

I seem to recall someone mentioning some way in which they react being really bad for MPDTs.